Star Trek: 10 Things You Didn’t Know About Sarek
1. Yesterday's Enterprise Was Originally His First Appearance In The Next Generation
Prior to Sarek's reappearance in his eponymous episode during The Next Generation, he was a key part of an initial story treatment for the critically acclaimed Yesterday's Enterprise.
In the episode, the Enterprise-C travels to the present through a temporal anomaly, and its absence from the past inadvertently leads to all out war between The Federation & The Klingons. However, the episode's initial pitch instead features Sarek using the time travelling Guardian of Forever to study ancient Vulcan at The Time of Awakening.
Before returning to the present, Sarek and his team would inadvertently alter the timeline leading to the death of Surak, the father of modern Vulcan, destabilising the planet and the wider galaxy as a result. Coming face to face with a fundamentally different Picard, Sarek would convince him to allow him passage back through time and take Surak's place in history, restoring the timeline to its rightful state.
Sarek's appearance was ironically vetoed by Micheal Tiller (who himself would bring Sarek back in the same season) for being gimmicky, and the episode was rewritten, like the timeline itself, to become one of The Next Generation's most well regarded episodes.